get the date right...

Fill in release date for 2.15

Fetch new translations from Transifex

Add dedicated release notes section for Windows high contrast mode su…

…pport (wagtail#7618)

Fill in release date for 2.14.2

Fill in release date for 2.13.5

fill in release date for 2.14.1

Version bump to 2.14 final

Version bump to 2.14rc1

Version bump to 2.13.4